Leaf spring suspensions have been developed long time ago and used extensively in many off-road applications but very little changes ever been made to them. In many cases a leaf spring was used primarily as a connecting member (to carry weight of a machine) more so than as a device to isolate and dampen vibration of those machines. A leaf spring alone has little capability to isolate vibration and cushion the ride especially if loads are heavy and terrains are rough. This is mainly due to the fact that a leaf spring member is often subject to forces and bending moments that are imposed in different directions during operation of the vehicle but the design of a simple one-element member simply does not allow flexibility required for proper functioning of a suspension to overcome these simultaneous loads and at the same time to respond and react to them differently and independently. That is why a typical leaf spring used in an off-road application is and has to be very rigid. Consequently the ride quality of the vehicle that uses such springs is more often rough, especially in the empty condition. There is no energy absorbing medium to dampen shocks and reduce natural frequency of vibration of the sprung mass. The spring rate of steel leaf springs is linear and therefore the vibration frequency of the sprung mass significantly changes from empty to loaded conditions.
Springs are a limited life component. They deform (bend or twist) permanently and eventually fail due to fatigue caused by overloading or repeated loading and other unpredictable conditions that may occur. A leaf spring is a homogeneous single-element entity. Once it is cracked, bent, twisted, or broken, the entire leaf needs to be replaced. When that happens it is also very likely that other springs which work with it need to be replaced as well simply because once one spring bends, fails, or is out of service, the others need to carry the additional load and will most likely be impacted by the overload caused by the failure of the first spring. It is also due to the fact that there is no adjustments that can be made to the others to bring them to the same height/orientation of the new spring. The downtime costs plus the cost to service and replace springs could be very expensive.